scholarly journals The growth of DM and DE perturbations in DBI non-canonical scalar field scenario

2020 ◽  
Vol 422 ◽  
pp. 168299
Author(s):  
K. Rezazadeh ◽  
S. Asadzadeh ◽  
K. Fahimi ◽  
K. Karami ◽  
A. Mehrabi
Keyword(s):  
Scalar Field ◽  
Canonical Scalar Field

scholarly journals Nonlinear Schrödinger-type formulation of scalar field cosmology: Two barotropic fluids and exact solutions

2020 ◽  
Vol 35 (19) ◽  
pp. 2050157
Author(s):  
Chonticha Kritpetch ◽  
Jarunee Sanongkhun ◽  
Pichet Vanichchapongjaroen ◽  
Burin Gumjudpai
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Time Dependent ◽  
Frw Cosmology ◽  
Dependent Case ◽  
Nonlinear Schrödinger ◽  
Barotropic Fluids ◽  
Scalar Field Cosmology ◽  
Formulation Variables ◽  
Canonical Scalar Field

Time-independent nonlinear Schrödinger-type (NLS) formulation of FRW cosmology with canonical scalar field is considered in the case of two barotropic fluids. We derived Friedmann formulation variables in terms of NLS variables. Seven exact solutions found by D’Ambroise [Ph.D. thesis, arXiv:1005.1410 ] and one new found solution are explored and tested in cosmology. The result suggests that time-independent NLS formulation of cosmology case should be upgraded to the time-dependent case.

scholarly journals Canonical scalar field inflation with string and R2-corrections

2021 ◽  
Vol 424 ◽  
pp. 168359
Author(s):  
S.D. Odintsov ◽  
V.K. Oikonomou ◽  
F.P. Fronimos
Keyword(s):  
Scalar Field ◽  
Canonical Scalar Field

scholarly journals α-Attractors and reheating in a nonminimal inflationary model

2020 ◽  
Vol 29 (10) ◽  
pp. 2050077
Author(s):  
R. Shojaee ◽  
K. Nozari ◽  
F. Darabi
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Parameter Space ◽  
Model Potential ◽  
Index Formula ◽  
Inflationary Model ◽  
Scalar Spectral Index ◽  
Canonical Scalar Field

We study [Formula: see text]-attractor models with both E-model and T-model potential in an extended Nonminimal Derivative (NMD) inflation where a canonical scalar field and its derivatives are nonminimally coupled to gravity. We calculate the evolution of perturbations during this regime. Then by adopting inflation potentials of the model we show that in the large [Formula: see text] and small [Formula: see text] limit, the value of the scalar spectral index [Formula: see text] and tensor-to-scalar ratio [Formula: see text] are universal. Next, we study reheating after inflation in this formalism. We obtain some constraints on the model’s parameter space by adopting the results with Planck 2018.

scholarly journals THE PHYSICS OF 2D STRINGY SPACETIMES

1992 ◽  
Vol 01 (02) ◽  
pp. 335-354 ◽  
Author(s):  
G.W. GIBBONS ◽  
MALCOLM J. PERRY
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
String Theory ◽  
Nontrivial Solution ◽  
Heterotic String ◽  
Two Dimensional ◽  
Dilaton Field ◽  
Black Hole Spacetime ◽  
Canonical Scalar Field

We examine the two-dimensional spacetimes that emerge from string theory. We find all of the solutions with no tachyons, and show that the only nontrivial solution is the black-hole spacetime. We examine the role of duality in this picture. We then explore the thermodynamics of these solutions which is complicated by the fact that only in two spacetime dimensions is it impossible to redefine the dilaton field in terms of a canonical scalar field. Finally, we extend our analysis to the heterotic string, and briefly comment on exact, as opposed to perturbative, solutions.

scholarly journals Anisotropic constant-roll inflation for the Dirac–Born–Infeld model

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Duy H. Nguyen ◽  
Tuyen M. Pham ◽  
Tuan Q. Do
Keyword(s):  
Scalar Field ◽  
Electromagnetic Fields ◽  
Canonical Extension ◽  
Numerical Calculations ◽  
Anisotropic Constant ◽  
Inflationary Phase ◽  
Canonical Scalar Field

AbstractIn this paper, we study a non-canonical extension of a supergravity-motivated model acting as a vivid counterexample to the cosmic no-hair conjecture due to its unusual coupling between scalar and electromagnetic fields. In particular, a canonical scalar field is replaced by the string-inspired Dirac–Born–Infeld one in this extension. As a result, exact anisotropic inflationary solutions for this Dirac–Born–Infeld model are figured out under a constant-roll condition. Furthermore, numerical calculations are performed to verify that these anisotropic constant-roll solutions are indeed attractive during their inflationary phase.

scholarly journals Intermediate inflation with non-canonical scalar field in the low anisotropy Universe

2019 ◽  
Vol 34 (33) ◽  
pp. 1950272
Author(s):  
Mahdieh Naderi ◽  
Ali Aghamohammadi ◽  
Abdollah Refaei ◽  
Haidar Sheikhahmadi
Keyword(s):  
Scalar Field ◽  
Bianchi Type ◽  
Type I ◽  
Spectral Indices ◽  
Common Procedure ◽  
Bianchi Type I ◽  
Good Consistency ◽  
Bianchi Type I Universe ◽  
Homogeneous Universe ◽  
Canonical Scalar Field

The behavior of a non-canonical scalar field within an anisotropic Bianchi type I, spatially homogeneous Universe in the framework of the intermediate inflation will be studied. It will be examined on the condition that both the anisotropy and non-canonical sources come together if there is any improvement in compatibility with the observational data originated from Planck 2015. Based on this investigation, it can be observed that automatically a steep potential which can manage inflation in a better way will be obtained. Additionally, as a common procedure for an inflationary study, we shall try to calculate the related inflationary observables such as the amplitude of the scalar perturbations, scalar and tensor spectral indices, tensor-to-scalar ratio, the running spectral index and the number of e-folds. As an exciting part of our results, we will find that our model has a good consistency compared to data resulting from CMB and different Planck results. To justify our claims, the well-known canonical inflationary scenario in an anisotropic Bianchi type I Universe will also be evaluated.

A non-canonical scalar field cosmological model: Stability and bifurcation analysis

2019 ◽  
Vol 34 (32) ◽  
pp. 1950261
Author(s):  
Sudip Mishra ◽  
Subenoy Chakraborty
Keyword(s):  
Phase Transition ◽  
Scalar Field ◽  
Critical Points ◽  
Autonomous System ◽  
System Analysis ◽  
Field Equations ◽  
Model Stability ◽  
Change Of Variables ◽  
Manifold Theory ◽  
Canonical Scalar Field

In this work, cosmological implications of a non-canonical scalar field model have been studied in the background of homogeneous and isotropic flat FLRW spacetime by using dynamical system analysis. By suitable change of variables, the field equations are transformed to an autonomous system and the stability of the system of critical points are examined. For hyperbolic critical points, the analysis of the system is done by using Hartman–Grobman theorem, while the center manifold theory is used to study non-hyperbolic critical points. It is found that the parameters in the autonomous system play a crucial role for phase transition of the Universe. Finally, possible bifurcation scenarios are discussed to identify the point of phase transition.

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